Polishing and diamond-truing machine for photoengraving

ABSTRACT

A polishing and diamond-truing machine for photoengraving cylinders wherein a frame on which a photoengraving cylinder is rotatably supported and operatively controlled in order to be machined by a diamond-truing tool unit mounted on an arm projecting transverse to said frame.

United States Patent inventor Giorgio Andreotti Via Don Gnocchi, 29 Milan, Italy AppL No. 4,590 Filed Jan. 21, 1970 Patented Dec. 28, 1971 Priority June 20, 1969 Italy 18477 A/69 POLISHING AND DIAMONDTRUING MACHINE FOR PHOTOENGRAVING 6 Claims, 5 Drawing Figs.

US. Cl 51/5 B241) 7/00 Field of Search 5 1 /5, 3, 129, 13 1; 29/27 C, 28

Primary Examinerwilliam R. Armstrong Attorneys-Guido Modiano and Albert losif ABSTRACT: A polishing and diamond-truing machine for photoengraving cylinders wherein a frame on which a photoengraving cylinder is rotatably supported and operatively controlled in order to be machined by a diamond-truing tool unit mounted on an arm projecting transverse to said frame.

PATENTED M82818?! SHEET 1 BF 3 INVENTOR.

GIORGIO AN DREOTTI INVENTOR.

GIORGIO A N DREOTTI AGENTAS 4 POLISHING AND DIAMOND-TRUING MACHINE FOR PHOTOENGRAVING BACKGROUND OF THE INVENTION This invention relates to a polishing and diamond-truing machine for photoengraving cylinders used in rotogravure printing.

It is known that these cylinders after having been copper plated must be of perfectly smooth surface, must be cylindrical and must correspond to the required size, with centesimal tolerances. According to the working methods used for preparing the cylinders, the case can also arise in which the cylinder surface has to be treated in order to eliminate all traces of the preceding engraving. This treatment, commonly call turning or truing or dressing and polishing", comprises normally a truing operation with the use of a diamond truer hereinafter called diamond-truing operation and a polishing operation, which are known for their laboriousness and delicacy, requiring the use of qualified personnel. By means of the diamond-truing operation a very high degree of exactitude of size and shape of the worked cylinder is obtained by removing a thin surface layer of the order of microns from the entire cylindrical surface of he cylinder. By means of the polishing operation a mirrorlike polished surface is obtained. These operations were heretofore carried out on separate machines since each of said operations poses different problems and different requirements to be satisfied.

SUMMARY OF THE INVENTION The main object of this invention is to provide a machine having structural characteristics such that a diamond-truing operation and a polishing operation can be carried out by the same machine and even simultaneously with substantial reduction in working time.

A further object is to provide the machine with such characteristics that the polishing mandrel may work at velocities which are considerably superior to the maximum velocities possible with conventional polishing machines, thereby further reducing the working time.

A further object of the invention is to provide a machine of the above type in which the combining of the diamond-truing and polishing operations does not affect in any way the desired and required degree of machining precision of the cylinders. In addition, by virtue of information as a monolithic complex which is particularly stable during operation and by allowing to avoid the use of auxiliary devices or apparatus which might in some way transmit to it vibrations or stresses which would lessen said degree of precision, it permits the attainment of improved results with respect to those presently attainable with machines of conventional type.

A still further object of this invention is that of providing a polishing and diamond-truing machine of the above type comprising considerable improvements in the polishing head, improvements which include particular clamping members for the abrasive sheet which is mounted on said head. In fact one of the disadvantages met with in conventional machines relates to said fixing members for the abrasive sheets, which generally do not clamp the sheets sufficiently during operation of the machine, leading to evident detriment to the quality of the polishing operation. These and further objects, which will better appear hereinafter, are attained by a polishing and diamond-truing machine for photoengraving cylinders, utilized in rotogravure machines, comprising a frame forming a bed bounded by lateral shoulders of said frame, a nose and tailstock cooperating in rotatably supporting a photoengraving cylinder and joined to said frame above said bed, at least said tailstock being mounted on a saddle slidable longitudinally with respect to said bed, in which the polishing and diamond truing machine comprises a plurality of cylindrical bias supported by said shoulders longitudinally behind said bed, a diamond-truing assembly and a polishing assembly independently and slidingly supported by said cylindrical bars whose diamond-truing and polishing tool holders respectively are adjustably positioned in a direction substantially transverse to said bed, a traverse screw for said diamond-truing assembly and a traverse screw for said polishing assembly rotatably supported by said shoulders and located at the back of said bed and parallel with said cylindrical bars, motor assemblies being provided for driving said traverse screws and for driving the polishing head or tool of said polishing assembly.

BRIEF DESCRIPTION OF THE DRAWING Further characteristics and advantages of the invention will better appear from the detailed description of a polishing and diamond-truing machine according to the invention, illustrated by way of example in the accompanying drawings in which:

FIG. 1 is a perspective frontal view of a polishing and diamond-truing machine according to the invention;

FIG. 2 is the same polishing and diamond-truing machine as seen from behind, on a reduced scale;

FIG. 3 is a sectional view on an enlarged scale of the polishing head of the polishing assembly used in the machine according to the invention, taken according to the axis of rotation to the polishing head.

FIG. 4 is a partially sectional frontal view of the same polishing head, the section being taken on line IV-IV of FIG.

FIG. 5 is an enlarged perspective view of the polishing assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2, the polishing and diamond-truing machine for photoengraving cylinders subsequently utilized in rotogravure comprises a frame I defining a bed bordered laterally by shoulders 2 and 3 transversal to said frame. The nose 4 is rigidly secured to the shoulder 2 above the bed, and in cooperation with the tailstock 5 supports and rotates said photoengraving cylinder (not shown). Said tailstock 5 is supported by a saddle assembly 6, attached above said bed and slidably supported by cylindrical bars 7 and 8, running longitudinally with respect to said bed and supported at their extremities by said shoulders 2 and 3.

Behind said bed and longitudinally to it, the shoulders 2 and 3 of the frame 1 support a pair of cylindrical bars 9 and I0, and a pair of traverse screws 11 and 12.

The diamond-truing assembly indicated generally by the reference numeral 13 is slidably engaged on said cylindrical bars 9 and I0, and comprises a carriage I4 slidably supported by said cylindrical bars 9 and 10 defining an arm 15 at the top (FIG. I) which is essentially projecting in a direction transversal to the bed defined by the frame I. Said carriage 14 is further engaged, by known means not shown, with the traverse screw 12, the control for engaging said carriage with and disengaging it from said traverse screw 12 being indicated generally by reference numeral 16. A holder 17 for the diamond-truing tool is slidably attached to the projecting arm 15, said tool being approached to or withdrawn from the cylinder to be diamond trued by a control 18 shown diagrammatically. The traverse screw 11 is normally out of engagement with the diamond-truing assembly and does not interfere with it. The polishing assembly indicated generally by reference numeral 19 is slidably supported on the same cylindrical bars 9 and 10. This polishing assembly comprises a polishing carriage 20 slidably supported by said bars 9 and 10, and simultaneously engaged by known means with the traverse screw 11. The carriage 20 defines at the top an inclined resting plane 21, extending in a transversal direction to the frame 1. This plane 21 (FIG. 5) supports a cylindrical casing essentially in the form of a sleeve 22, in which is slidably mounted an electromandrel unit which, in its turn, supports at its electromandrel unit 23 which, in its turn, supports at its front the polishing head 24 suitably protected by a shield 25. The electromandrel unit 23 comprises an electromotor with a rotor in rigid rotatory relation with the electromandrel proper 30 and imparting rotation thereto. The motor 26 for positioning the electromandrel 30 and the controls connected with the handwheel 27 for micrometrically positioning said electromandrel 30, are mounted above the cylindrical casing 22. The locking lever 28 for the electromandrel and the flexible conduit 29 for feeding the polishing water are also shown. A measuring instrument 28a indicates the pressure exerted by the polishing head against the cylinder to be polished. This measuring instrument is advantageously based on an amperemeter measuring the electric current drawn by the electrometer during the polishing operation, the intensity of this current being substantially proportional to the power necessary for overcoming the friction created during the polishing operation.

FIGS. 3 and 4 shown the polishing head 24 in detail. The reference numeral 30 indicates the hollow extremity of the electromandrel proper into which the conical spigot 31 is removably inserted blocked by the key 32 and gudgeon pin 33 whose head is located in an annular guide defined by the ringnut 36 and the annular member 37, normally rotating rigidly with said ringnut 36. Said ring nut 36 and the annular member 37 are eccentrically mounted externally on said spigot 31 (P16. 4) so that the rotation of the group consisting of the ring nut 36 and annular member 37 gives rise to insertion or withdrawal of the pin 33 from the seat 33a provided in said spigot 31. For the purpose a peripheral slot is provided in the ringnut 36 allowing relative movement between pin 33 and ringnut 36 along the periphery of the latter. The spigot 31 of the polishing head is prolonged as an extension 38, which, together with the plate 39 fixed to it, supports the pad 40 on which the abrasive sheet 41 rests. This pad 40 is provided with rounded edges 42 so that the abrasive sheet 41 does not deteriorate. The extension 38 of the polishing head has an octagonal periphery as seen in FIG. 4. The means for clamping the sheet 41 on to the pad 40 are arranged on the four alternate sides of the extension 38. These clamping means each consist of a lever in the form of a plate 43 provided with bored lugs 44, which engage a pivot 45. This pivot 45, which constitutes the hinge between the lever 43 and the extension 38 is supported by supports 46 fixed by known means to the extension 38. A spiral spring coaxial to the pivot 45 and reacting with its extremity 48 on the extension 38, maintains the extremity 49 of the lever 43 pushed against the periphery of the extension 38, namely against the edge provided on said periphery. Said lever 43 is advantageously provided with a handle 42a on the side opposite the edge 42 for its manual operation against the spring 47. The hinge axis of the lever 43 on the extension 38 is located nearer to the extremity 49 of the lever than the center of gravity thereof. As is clearly seen in FIG. 3, the lever 43 holds the abrasive sheet 41 against the pad 40 between its extremity 49 and the ledge 50. in addition, during the rotation of the electromandrel 23, the centrifugal force that is exerted on said lever contributes towards pressing its extremity 49 against the corresponding leg 50 because of the positioning of the pivot 45 nearer to the edge 49 of said lever 43, than the center of gravity thereof, so increasing the clamping action due to the spring 47. A protection shield 51 for the polishing head 24 is fixed to the electromandrel 23, this shield being provided with a part 25 (FIG. which opens as a window for allowing inspection of the head 24 and application of the abrasive sheet 41, permitting the lever 43 to be operated in the way previously described.

ple during lishing rotational velocit for the mandrelof he order 0 1400 r.p.m. can be use while in polishing machines presently in commerce the mandrel can rotate at maximum velocities of -200 r.p.m.

I claim:

1. A polishing and diamond-truing machine for photoengraving cylinders utilized in photogravure machines, comprising a frame forming a bed bounded by lateral shoulders of said frame, a nose and tailstock cooperating in supporting a photoengraving cylinder and joined to said frame above said bed, at least said tailstock being mounted on a saddle slidable longitudinally with respect to said bed, the machine being characterized in that it further comprises a plurality of cylindrical bars supported by said shoulders longitudinally behind said bed, a diamond-truing assembly and a polishing assembly independently and slidingly supported by said cylindrical bars and whose diamond-truing and polishing tool holders respectively are adjustably positioned in a direction substantially transverse to said bed, a traverse screw for said diamond-truing assembly and a traverse screw for said polishing assembly rotatably supported by said shoulders and located at the back of said bed and parallel with said cylindrical bars.

2. A machine as claimed in claim 1, in which said diamondtruing assembly comprises a saddle slidably attached to said cylindrical bars and is removably engaged with said traverse screw of said diamond-truing assembly, an arm defined by the top of said saddle essentially projecting transverse to said bed, and a diamond-truing tool holder slidably and adjustably attached to said arm.

3. A machine as claimed in claim 1, in which said polishing assembly comprises a saddle slidably attached to said transversal bars and removably engaged with said traverse screw of the polishing assembly, said saddle defining an inclined support plane above said bed supporting an electromandrel extending substantially transverse to said bed and being adjustably positionable with respect to it, said electromandrel supporting a polishing head at one extremity.

4. A machine as claimed in claim 3 in which said removable polishing head attached to said extremity of said electromandrel by substantially eccentric cam means is provided with members for clamping an abrasive sheet which are provided with spring means which removably lock said sheet against a platelike member attached to said head, of which it constitutes an integral part, said substantially plierlike clamping members being subjected during the rotation of said head to a centrifugal force which cooperates with said spring means in locking said abrasive sheet.

5. A machine as claimed in claim 4, in which said polishing head is of polygonal profile and said clamping members are arranged on a plurality of the constituent side of said polygon.

6. A machine as claimed in claim 1, in which said saddle supporting said tailstock is in its turn slidably supported by a pair of cylindrical bars attached at their extremities to said lateral shoulders of said frame. 

1. A polishing and diamond-truing machine for photoengraving cylinders utilized in photogravure machines, comprising a frame forming a bed bounded by lateral shoulders of said frame, a nose and tailstock cooperating in supporting a photoengraving cylinder and joined to said frame above said bed, at least said tailstock being mounted on a saddle slidable longitudinally with respect to said bed, the machine being characterized in that it further comprises a plurality of cylindrical bars supported by said shoulders longitudinally behind said bed, a diamond-truing assembly and a polishing assembly independently and slidingly supported by said cylindrical bars and whose diamond-truing and polishing tool holders respectively are adjustably positioned in a direction substantially transverse to said bed, a traverse screw for said diamond-truing assembly and a traverse screw for said polishing assembly rotably supported by said shoulders and located at the back of said bed and parallel with said cylindrical bars.
 2. A machine as claimed in claim 1, in which said diamond-truing assembly comprises a saddle slidably attached to said cylindrical bars and is removably engaged with said traverse screw of said diamond-truing assembly, an arm defined by the top of said saddle essentially projecting transverse to said bed, and a diamond-truing tool holder slidably and adjustably attached to said arm.
 3. A machine as claimed in claim 1, in which said polishing assembly comprises a saddle slidably attached to said transversal bars and removably engaged with said traverse screw of the polishing assembly, said saddle defining an inclined support plane above said bed supporting an electromandrel extending substantially transverse to said bed and being adjustably positionable with respect to it, said electromandrel supporting a polishing head at one extremity.
 4. A machine as claimed in claim 3 in which said removable polishing head attached to said extremity of said electromandrel by substantially eccentric cam means is provided with members for clamping an abrasive sheet which are provided with spring means which removably lock said sheet against a platelike member attached to said head, of which it constitutes an integral part, said substantially plierlike clamping members being subjected during the rotation of said head to a centrifugal force which cooperates with said spring means in locking said abrasive sheet.
 5. A machine as claimed in claim 4, in which said polishing head is of polygonal profile and said clamping members are arranged on a plurality of the constituent sides of said polygon.
 6. A machine as claimed in claim 1, in which said saddle supporting said tailstock is in its turn slidably supported by a pair of cylindrical bars attached at their extremities to said lateral shoulders of said fraMe. 